The ATtiny85 is an incredible piece of engineering. In just eight pins, you get a microcontroller with just enough oomph to do some really heavy lifting. You get an Open Source toolchain, and if you’re really good, you can build your own programmer. It does have its limits though; there isn’t a whole lot of Flash, and of course you’re always going to need a few extra pins.
For his Hackaday Prize entry, [danjovic] is pushing whatever limits are left with the ‘tiny85. He’s using it as a test pattern generator, pushing out pixels to any old TV. The entire circuit is powered by a coin cell, and the entire thing fits in a Tic-Tac box.
The heart of the project, as you would expect, is a resistor ladder using all six available pins, using five for luminance and one for the sync. That is thirty-two shades of gray, if you’re keeping track. The trick is using the internal PLL and a bit of math to calculate the proper resistor values. The result is just a test pattern, yes, but [danjovic] managed to get a test pattern that has a resolution of 850 pixels across. That’s not bad by any measure.